Optical communication involves imprinting or encoding information on light, thereby adapting the light to carry or convey the information as the light propagates or travels between two sites. The two sites may be across the globe or across a country, a state, a town, or a room, for example.
Imprinting or encoding information on light typically involves varying, modulating, or changing some attribute or aspect of the light over time to create a pattern representing the information. A sender or transmitter of the information imposes the pattern on the light, and a receiver of the information identifies the pattern and thereby receives the information.
For example, sailors on two distant ships may communicate with one another with powerful flashlights. One sailor pulses light on and off in a sequential pattern that represents letters of the alphabet, forming words and sentences, for example in Morse code. The other, distant sailor watches the light and notes the on-off pattern. Knowing the on-off sequences of each letter, that distant observer sailor determines the letters, words, and sentences via reversing the code. While modern fiber optic communication systems are more sophisticated than sailors sending messages to one another with flashlights, the basic concept is generally analogous.
A fiber optic communication system may comprise terminals or users linked together via optical paths, for example in a fiber optic network. Each terminal may comprise a transmitter and a receiver that may be components of a transceiver. Alternatively, a terminal may comprise a receiver without a transmitter. Each transmitter typically outputs light imprinted or encoded with information destined for receipt at a remote terminal. Meanwhile, each receiver typically receives light that has been imprinted or encoded with information at another, remote terminal. Accordingly, devices on an optical network can communication with one another via sending and receiving optical signals.
In certain conventional approaches known as WDM, coarse WDM (“CWDM”), and dense WDM (“DWDM”), a single optical path (often an optical fiber provides the transmission medium) concurrently conducts multiple optical signals, each carrying different information in a different wavelength band. Each wavelength or color provides an information channel. As a result, the optical path has an aggregate bandwidth or information carrying capability that is a multiple of the individual WDM, CWDM, or DWDM channel's bandwidth or information carrying capability.
Conventionally, a system of one or more optical filters manipulates the incoming light according to color. The filtering system diverts each of the WDM, CWDM, or DWDM channels to a dedicated detector. Thus, one detector exclusively receives one optical signal in an assigned wavelength band, while another detector exclusively receives another optical signal in another assigned wavelength band. Each channel has one assigned detector, and each detector has one assigned channel. The filtering system generally prevents a single detector from receiving two or more WDM, CWDM, or DWDM signals concurrently. With conventional technology, any incoming photons of one WDM, CWDM, or DWDM signal that might be received as stray light by a detector assigned to a different WDM, CWDM, or DWDM signal are generally inadvertent, unwanted, and detrimental. Accordingly, signal separation occurs in the optical domain.
An issue with the conventional receiver technology described above concerns optical filtering. Many conventional optical filtering systems, whether based on thin-film interference, arrayed waveguide gratings, or fiber Bragg grating technologies, are more expensive than applications with tight cost constraints can tolerate. Often, a significant portion of the expense is associated with meeting optical performance specifications requiring strict separation of WDM, CWDM, or DWDM optical signals. In other words, manufacturers typically go to great lengths to make filtering systems that prevent all but the smallest level of light of one wavelength from spilling into a detector assigned to another wavelength.
In view of the aforementioned representative deficiencies in the art (or some other related shortcoming), need exists for an improved optical communication system that can separate optical signals of differing wavelengths via electrical signal processing. Another need exists for a technology that can relax filtering specifications and/or that can utilize filtering devices that fail to meet tight filtering performance specifications. Further need exists for a WDM, CWDM, or DWDM receiver comprising multiple detectors that are each assigned to receiving multiple optical signals of different wavelengths. A technology addressing one or more such needs would benefit optical communications, for example via providing lower cost, better access to higher bandwidth, new applications, reduced size, lower power consumption, higher levels of integration, better manufacturability, etc.